Method of and apparatus for telemetering information from a point in a well borehole to the earth&#39;s surface

ABSTRACT

Down-hole information from rotary well drilling operations is transmitted to a surface or remote location by the venting of drilling fluid from the interior of the drill stem into the bore hole annulus in a binary coded decimal format. A valve is caused to operate by the digital output of one or more down-hole transducers thus releasing and restoring the drilling fluid pressure in the desired sequence. A &#34;sub&#34; contains the necessary electronics, power supply and a motorized valve assembly. Commands from the surface to transmit information from any one of the transducers are transmitted by means of sequential pulses in a binary coded decimal format, in the drilling fluid pressure are provided by the operator by deliberately decreasing and then increasing the surface pump pressure in a sequence to which the applicable down-hole actuating means is responsive.

BACKGROUND OF THE INVENTION

This invention relates to new and useful improvements in rotary welldrilling operations and provides the means for transmitting desireddown-hole imformation to the surface by causing the drilling rig pumppressure to depart from its normal level in sympathy with digitalsignals derived at a down-hole location. This is accomplished by theventing of drilling fluid from the interior of the drill stem into theborehole annulus in a binary coded decimal format, by means of a valvethat is caused to operate by the digital output of one or more down-holetransducers.

In exploring for crude oil and natural gas, it is the present practiceto drill wells into the earth using a "rotary" drilling technique. Underthese circumstances, the drilling apparatus includes means whereby adrill string (consisting of a number of sections of hollow pipe andhaving a drill bit connected to the lower end) is caused to rotate,while the amount of axial force applied to the bit is carefullycontrolled.

While the well is being drilled, it is common practice to circulatedrilling fluid (some mixtures of which are colloquially known as "mud")down through the hollow drill string, through restrictive nozzles in thebit, and back to the earth's surface through the annulus of theborehole. Upon reaching the earth's surface, the drilling fluid(containing the cuttings from the drill bit) is allowed to flow througha screening device into a series of tanks from which it is recirculatedthrough the borehole. Besides providing the vehicle whereby cuttings arereturned to the surface, the drilling fluid acts to cool and lubricatethe drill bit and the exterior of the drill string. Also the drillingfluid prvides a back pressure in the hole to more or less containnatural gas that may be encountered during the drilling process.

For the fluid to provide the required cleaning and cooling action withrespect to the drill bit, the bit is constructed to include a number ofnozzles (typically three) through which the fluid is forced atrelatively high pressures. To accommodate the need for such drillingfluid pressures, the drilling apparatus includes pumps, piping, and therequired swivel joint to permit the entry of the fluid into the rotatingdrill string.

It has become increasingly apparent to the producers of crude oil andnatural gas, that means must be found to increase the efficiency ofdrilling operations in order to offset sharply rising costs. In part,the increased costs are due to the need to explore in geographical areasthat are more and more remote from the markets for petroleum products.

Those skilled in the art of drilling wells recognize that the efficiencywould improve significantly if some means could be found whereby theyare advised of conditions at the bottom of the hole while drilling is inprogress. For example, the bit may encounter a sloped sub-surfaceformation causing it to depart from the vertical and commence drillingat an angle. Or if excessive weight is inadvertently applied to the bit,the drill string will bend, again causing the hole to depart from thevertical. If the bore-hole is allowed to progress at an angle withrespect to the vertical, the "target" zone may be missed altogether, andthe drill string will be exposed to excessive wear due to the tangentialrubbing action at the point of hole curvature.

To determine whether or not the bore-hole has departed from thevertical, it is the present practice to periodically stop drilling whilea "survey" is conducted. Typically, a survey is carried out by loweringa recording inclinometer (EG: one in which the position of pendulum isphotographed) down the interior of the drill string on electricallyconducting wires.

Alternatively, an instrument responsive to inclination and triggered bya clockwork mechanism may be dropped into the drill string and recoveredlater. The former technique is expensive and time consuming, andnecessitates the stopping of fluid circulation--which emphasizes thepossibility of the drill string becoming stuck in the hole. The lattertechnique will only provide information considerably after the fact, andif the instrument happened to encounter an obstruction en route to thebottom of the hole, the clockwork mechanism may have triggered therecording too soon, thereby providing seriously misleading information.

To facilitate further research into well drilling operations, it wouldbe useful to have other information (EG: temperature, pressure, weighton bit, etc.) telemetered from the bottom of the hole while wells arebeing drilled. This information would be used to more accurately predictthe performance of various types of bits, the likelihood of encounteringa gas bearing formation, the optimization of table RPM and weight on thebit to achieve maximum penetration rate, the mixture of mud that shouldbe used, and the like.

Clearly, then, an instrument that will effect the transmission ofdown-hole information to the earth's surface, dependably, without theuse of wire lines, would provide drillers with the means tosignificantly improve the efficiency of their operations.

Numerous attempts have been made to build a device that will providewireless transmission from a down-hole location to the earth's surface.For example, various systems based upon the transmission of acousticalwaves through the steel drill string or through the drilling fluid havebeen described in the prior art. However, such factors as theattenuation of the signals by the drill string immersed in the drillingfluid, bubbles in the drilling fluid, the ambient noise in the drillingapparatus, the hostility of the down-hole environment (with respect totemperature, pressure, and vibration), the transfer of energy fromtransducers into the transmission medium, the need for transducers intothe transmission medium, the need for relatively large amounts ofelectrical power in the down-hole apparatus, and the need for "ruggedsimplicity," have, insofar as the applicants are aware, precluded thereduction of such prior art to actual use.

SUMMARY OF THE INVENTION

It is the broad object of the present invention to solve problemsencountered in the prior art with respect to the transmission ofinformation from a point in a well bore-hole to the earth's surface.This is accomplished by means of a down-hole valve assembly that permitsdrilling fluid to exit from the interior of the drill string and enterthe bore-hole annulus, such that the pressure applied to the drillingfluid by the surface pumps will experience a significant decrease eachtime the valve is opened.

Transmission of information from the down-hole location is effected byselectively opening and closing the valve in sympathy with logical onesand zeroes that are obtained electronically from sub-surfacetransducers. At the earth's surface, the transmitted information isreceived by electronically detecting the variations in pump pressurecaused by the opening and closing of the downhole valve. Therefore,under conditions of dynamic drilling fluid circulation, information istransmitted from a down-hole location to the earth's surface.

Another object of the present invention is to provide means whereby thedown-hole instrumentation and valve assembly can be actuated on commandfrom the surface. If the driller wishes to interrogate a sub-surfacetransducer that is included as an input means to the present apparatus,he can do so by deliberately decreasing and then increasing the surfacepump pressure in a sequence to which the applicable down-hole actuatingmeans is responsive.

With the foregoing objects in view, and other such objects andadvantages as will become apparent to those skilled in the art to whichthis invention relates as this specification proceeds, .[.my.]..Iadd.our .Iaddend.invention consists essentially in the arrangement andconstruction of parts all as hereinafter more particularly described,reference being had to the accompanying drawings in which:

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified schematic view showing the rotary drillingtechnique, including the sub-surface instrumentation and transmitting"sub" of the present invention.

FIG. 2 is a block diagram of the surface electronic circuitry.

FIG. 3 is a schematic side elevation of the instrumentation andtransmitting "sub".

FIG. 4 is a cross section substantially along the line 4--4 of FIG. 3.

FIG. 5 is a cross-sectional schematic view showing the interior of theinstrumentation and transmitting "sub" and taken substantially long theline 5--5 of FIG. 3.

FIG. 6 is a diagram of the voltage analog of pump pressue vs time asdetected by the surface receiving apparatus with the down-hole valveclosed.

FIG. 7 is a diagram of the voltage analog of pump pressure vs time asdetected by the surface receiving apparatus with the down-hole valveopened, and closed.

In the drawings like characters of reference indicate correspondingparts in the different figures.

DETAILED DESCRIPTION

Referring now to the drawings and more particularly to FIG. 1, there isshown therein a simplified sketch of the apparatus used in aconventional rotary drilling rig. The drill string collectivelydesignated 10, consists of a drill bit 11 affixed to the lower end, oneor more drill collars 12, having a greater weight and greater meandiameter than the sections of drill pipe 13, and a "kelly" 14 having apolygon cross section.

A rotary table 15 includes a centrally located polygon shaped hole (notillustrated) to loosely accommodate the kelly 14, such that rotationalmovement of the table 15 causes the kelly 14, and hence the entire drillstring 10, to rotate. The drill collars 12 are included to increase theweight of the drill string, such that the overall center of gravity ofthe drill string is located towards the bottom end.

The top end of the kelly 14 is connected to a swivel joint 16 which, inturn, is connected to a supporting hook 17. The hook is affixed to thetravelling block of a "block and tackle" assembly (not illustrated)whereby the drill string 10 may be raised and lowered by means of arig's draw-works. The swivel joint 16 permits the drill string to rotatewhile the hook 17 remains fixed; it also affords a means wherebydrilling fluid can be injected into the interior of the drill stringfrom a flexible mud stand-pipe 18.

The drilling fluid (mud) circulation system consists of one or morepumps (not illustrated) used to force the mud through the stand-pipe 18,through the interior of the drill string 10, through restrictive nozzles11A in the drill bit 11, through the annulus 19, back to the earth'ssurface, and through a mud output flow line 20 into a series of tanks(not illustrated). The input of the pump is effected by means of asuction line into one of the mud tanks (not illustrated) therebycompleting the circulatory system. All of the foregoing apparatus isconventional.

FIG. 1 shows the down-hole assembly or "sub" portion 21 of the presentinvention as it may be installed in the drill string 10 (typically)above the drill bit, and containing the electronic, electrical, andmechanical devices hereinafter to be described.

In FIG. 2, there is shown an arrangement of electronic circuitry that ispart of the present invention and is located in some convenient place inthe "on surface" rig's quarters. This circuitry operates in conjunctionwith the down-hole apparatus to receive, decode and read-out theinformation that is telemetered from the sub-surface location. Also, thesurface installation includes a means of electronically interpreting thevariations in pump pressure so as to facilitate the interrogation of thedown-hole apparatus.

In particular, 22A is a "pressure to Voltage" transducer, well known inthe art, that provides an output voltage having a magnitude that ispredictably related to the pressure of the drilling fluid in the pipingbetween the pump and the swivel joint 16. The analog signal indicativeof pump pressure is processed by the pressure transducer electronics 22Bfor subsequent receive/decode treatment 22C and presentation in analogand/or digital formats in such devices as strip chart recorders andin-line digital displays 22D. The interrogation module 22E is typicallylocated within the range of vision of the driller while he is operatingthe rig's controls. This interrogation module presents the driller witha visual indication of the ON/OFF pumping events he is to follow inorder to interrogate the down-hole detection and transmission means.Typically, the interrogation module 22E will respond to the output ofthe pressure transducer 22A such that in a series of six lamps (notillustrated), the first is illuminated when the pump pressure decreasesan amount consistent with the sensitivity of the down-hole pressuredetecting means. Observing that the first lamp is lit, the drillerre-energizes the motor driving the pump, and the subsequent pressureincrease is detected by the transducer 22A. When said pressure increasesan amount consistent with the down-hole system's upper pressure responsepoint, the second lamp in the interrogation module's series isautomatically illuminated, advising the driller that the interrogationsequence requires him to again cause a pressure decrease byde-activating the pump. By responding to the ON/OFF commands of thelamps within a predetermined time period (typically 30 seconds) thedriller has created a series of pressure variations or "pulses" to whichthe down-hole instrumentation is responsive. This constitutes the remoteinput means operatively connected to the drilling fluid circulationsystem to decrease and then increase the associated pump pressure in asequence to which said means to open and close said valve is responsive,and referred to in some of the claims. The result of such interrogationis to activate an asynchronous down-hole detection/transmissionapparatus such that the magnitude of the selected sub-surface parameteris reported to the surface by the means herein described. As thecircuitry for the lamp is well known, it is not deemed necessary toillustrate same. Furthermore other indicating devices could be used.

In FIG. 3, there is shown an exterior view of the down-holeinstrumentation and transmitting "sub" 21 of the present invention, andin FIG. 5 there is shown an interior view (section 5--5) of the "sub".

Referring now to FIG. 5, the drilling fluid flows downward through thewash-pipe 23 that has an offset section 23A for the purpose of providingspace for the electro/mechanical sub-systems of the present invention.

The down-hole instrumentation is in a quiescent state until it isactuated by a command from the surface as previously described. Themeans whereby the down-hole instrumentation is responsive to the"command" pressure variations includes a rate of pressure change (dp/dt)switch 24 contained in an electro/mechanical cavity 30, with associatedelectronic circuitry contained in an annular electronic cavity 25. The(dp/dt) switch 24 is responsive to the time rate of change of drillingfluid pressure. This switch, which is conventional, will operate if, andonly if, the pressure of the drilling fluid changes a predeterminedamount in a fixed time interval.

Having accepted the activating command from the surface, the down-holeinstrumentation will carry out, automatically, the following sequence:

(a) Energize a transducer (EG: Temperature to voltage) contained in thetransducer housing 26.

(b) Convert the voltage analog (the output of the transducer) to adigital word, in which binary 1's and 0's are identified by discretevoltage levels. This digital word is then temporarily stored in a shiftregister (not illustrated) in the electronic cavity 25.

(c) In a timing sequence consistent with the practicality of the system,serialize the digital word by applying clock pulses to the shiftregister.

(d) By means of buffering and power amplifiers, (not illustrated) usethe serial digital word to activate the motor of the motor/valve 27,whereby a portion of the drilling fluid is permitted to exit from thewash-pipe 23 and enter the annulus 19 without having passed through therestrictive nozzles in the drill bit 11. Because the valve is actuatedby the digital word derived from the transducer, the releasing of thedrilling fluid from the wash-pipe to the annulus will occur in asequence of GO/NO-GO events indicative of the physical measurement madeby the transducer.

The electrical power required to carry out the foregoing operations isprovided (typically) by a battery of dry cells (not illustrated)contained in the annular power supply cavity 28. Electrical cabling 29is used to interconnect the various components and devices constitutingthe instrumentation package. The three functional cavities 25, 28 and 30are separated by means of seals 31 and 32. Alternatively, it ispreferable that these cavities or components are each a self-containedmodule having closed ends, and screw threadably connected together toform the complete "sub" 21, in order to isolate the cavities from oneanother in the event that a seal 31 ruptures for example, as thedrilling fluid would damage or destroy the electronics and/or powersupply.

In the event that a plurality of down-hole measurements are to be made,the apparatus is expandable to include sampling and multiplexingcircuitry (well known in the electronics art) such that a series ofidentifiable digital words, each word reflecting the output of aspecific measurement transducer, may be used to activate the valve 27 ina sequential manner as previously described.

Having established that the present apparatus will, on command from thesurface; cause a portion of the drilling fluid to be sequentiallyreleased from the interior of the drill string 10 into the annulus 19 insuch a way as to digitally conform to the measurement of physicalquantities in a down-hole location, we now proceed to a description ofthe means whereby the said digital information is transmitted to theearth's surface and there received and displayed.

In FIG. 6 there is shown a plot that is typical of PUMP PRESSURE vs TIMEas experienced in normal well drilling operations. The average pumppressure is shown to be 1000 psi, with cyclic variations above and belowthis value caused by the reciprocating motion of the piston in the pump.As previously mentioned, this pressure is applied to overcome theresistance offered by the nozzles in the drill bit 11.

In FIG. 7 there is shown a plot of the reaction of pump pressure whenthe down-hole valve 27 of the present invention is opened. Assuming thatthere are three nozzles 11A (of equal size) in the drill bit 11, andthat the valve controlled path affords a drilling fluid throughput (fromthe wash-pipe 23 to the annulus 19) that is equivalent to one of the bitnozzles, then the opening of the valve 27 will cause a net 25% decreasein pump pressure. In FIG. 7 the opening of the valve commences at t=5seconds and requires approximately 1 second to open fully. Commencing att=6 seconds, then, the average pump pressure is seen to be 750 psi. Att=8 seconds the valve starts to close, and is completely closed at t=9seconds, at which time the pump pressure returns to its original averagevalue of 1000 psi. At t=12 seconds the sequence is repeated. In each ofthe two cases, the valve is fully open for a total of 2 seconds.

The timing of the valve opening and closing events will be influenced byvarious factors and is therefore made variable in this apparatus. Forexample, a particular drillng rig may include a surge suppressor in thedrilling fluid circulating system, and this compressed air device willtend to integrate the pressure waves that form the basis for the presentcommunications medium. To overcome this effect, the down-hole valve iscaused to remain open for a period that compensates for the timeconstant of the integrating surge suppressor, and may, as a result,require a slightly longer time to transmit a given digital word.

In the present invention, a pressure to voltage transducer 22A isinstalled in the pipe 18A between the pump and stand-pipe 18. The objectof this transducer is to provide, on a continual basis, a voltage thatis analogous to the pressure applied to the drilling fluid by the rig'spump. The voltage output of this transducer is automatically monitoredby electronics circuitry 22B such that significant pressure decreases,caused by the opening of the down-hole valve 27 are detected.

Operating in conjunction with the transducer electronics there is asurface "RECEIVER" 22C as shown in FIG. 2. This receiver containselectronics circuitry that will establish, by means of timing pulses,the validity of the information as reported by the pressure transducer22A. If the information is valid, it will be processed by the receiver22C and subsequently transferred to a "read-out" means 22D in a formatthat is meaningful to the rig operator.

To summarize the present invention, a measurement of one or moredown-hole parameters is made and digitized; the digital word is used torelease drilling fluid from the interior of the drill string to theannulus in a sequence conforming to the digital word; the resultingdecrease in pump pressure is detected at the earth's surface, andpresented to the rig operator in a meaningful way.

Since various modifications can be made in our invention as hereinabovedescribed, and many apparently widely different embodiments of same madewithin the spirit and scope of the claims without departing from suchspirit and scope, it is intended that all matter contained in theaccompanying specification shall be interpreted as illustrative only andnot in a limiting sense.

What we claim as our invention is: .[.
 1. A method of telemeteringinformation from a point in a well bore-hole, to the earth's surfaceutilizing the drilling fluid pump pressure comprising the steps ofdetecting the information required, translating and transmitting saidinformation into digital signals, decreasing and then increasing thepump pressure by venting the drilling fluid in a binary coded decimalformat, by said digital signals, remotely detecting said decreases andincreases of drilling fluid pump pressure and then decoding anddisplaying the results of said increases and decreases of said drillingfluid pump pressure and hence the information detected, said translationand transmitting of the information being initiated by the additionalstep of first decreasing and then increasing the drilling fluid pumppressure at the surface in a predetermined sequence..]. .[.2. In a welldrilling rig which includes a hollow drill string assembly within abore-hole thereby defining a bore-hole annulus, a rotatable bit on thelower end of said hollow drill string, drill fluid restrictive nozzlesin said bit, a drilling fluid circulation system including a pump and asource of drilling fluid, and conduit means operatively connecting saidpump to said source of drilling fluid and to said hollow drill string;the improvement comprising in combination a down-hole assembly installedwithin the associated drill string, means to convey the associateddrilling fluid under pressure, through said assembly, a motorized valvewithin said assembly operatively connected between said means to conveyassociated drilling fluid through said assembly and the associatedbore-hole annulus when the valve is open and to shut off said lastmentioned means when said valve is closed, at least one informationresponsive transducer operatively connected to said assembly, electronicmeans in said assembly to translate information received by saidtransducer, into means to open and close said valve in a binary codeddecimal sequence thereby decreasing and increasing the drilling fluidpressure in said predetermined sequence, means remote from said assemblyto detect said decreases and increases in drilling fluid pressure andmeans to decode and display said detected decreases and increases indrilling fluid pressure, and a source of electrical power for saidassembly..]. .[.3. The assembly according to claim 2 which includes arate of pressure change switch operatively connected to said motorizedvalve whereby said valve only operates responsive to a decrease andincrease in pressure if the pressure of the drilling fluid changes apredetermined amount in a fixed time or period..]. .[.4. The assemblyaccording to claim 2 in which the assembly includes a cylindricalcasing, a drilling fluid conduit extending through said casing, anannular cavity defined between said conduit and said casing, saidconduit being offset through part of said casing, said casing includingan electronic holding section within said cavity, an electro-mechanicalholding section within said cavity adjacent said offset, and a powersupply holding section within said cavity, and means to seal off saidcavities one from the other, said casing being adjacently connectedwithin said drill string..]. .[.5. The assembly according to claim 2 inwhich said electronic means in said assembly translates informationreceived by said transducer into digital signals for opening and closingsaid valve..]. .[.6. The assembly according to claim 5 which includesremote input means operatively connected to said drilling fluidcirculation system to decrease and then increase the associated pumppressure in a sequence to which said means to open and close said valveis responsive thereby initiating the operation of said valve to signalinformation received from said transducer within said assembly, to saidmeans to decode and display said detected decreases and increases insaid drilling fluid pump pressure..]. .[.7. The assembly according toclaim 5 in which the assembly includes a cylindrical casing, a drillingfluid conduit extending through said casing, an annular cavity definedbetween said conduit and said casing, said conduit being offset throughpart of said casing, said casing including an electronic holding sectionwithin said cavity, an electromechanical holding section within saidcavity adjacent said offset, and a power supply holding section withinsaid cavity, and means to seal off said cavities one from the other,said casing being adjacently connected within said drill string..]..[.8. The assembly according to claim 3 in which the assembly includes acylindrical casing, a drilling fluid conduit extending through saidcasing, an annular cavity defined between said conduit and said casing,said conduit being offset through part of said casing, said casingincluding an electronic holding section within said cavity, anelectromechanical holding section within said cavity adjacent saidoffset, and a power supply holding section within said cavity and meansto seal off said cavities one from the other, said casing beingadjacently connected within said drll string..]. .[.9. The assemblyaccording to claim 5 which includes said means remote from said assemblycomprising a pressure-to-voltage transducer operatively connected tosaid conduit means between said pump and said hollow drill string,electronic means to receive and decode signals from saidpressure-to-voltage transducer, operatively connected to said transducerand readout means operatively connected to said electronic means..]..[.10. The assembly according to claim 9 which includes remote inputmeans operatively connected to said drilling fluid circulation system todecrease and then increase the associated pump pressure in a sequence towhich said means to open and close said valve is responsive therebyinitiating the operation of said valve to signal information receivedfrom said transducer within said assembly, to said means to decode anddisplay said detected decreases and increases in said drilling fluidpump pressure..]. .[.11. The assembly according to claim 2 whichincludes said means remote from said assembly comprising apressure-to-voltage transducer operatively connected to said conduitmeans between said pump and said hollow drill string, electronic meansto receive and decode signals from said pressure-to-voltage transducer,operatively connected to said transducer and read-out means operativelyconnected to said electronic means..]. .[.12. The assembly according toclaim 11 which includes remote input means operatively connected to saiddrilling fluid circulation system to decrease and then increase theassociated pump pressure in a sequence to which said means to open andclose said valve is responsive thereby initiating the operation of saidvalve to signal information received from said transducer within saidassembly, to said means to decode and display said detected decreasesand increases in said drilling fluid pump pressure..]. .[.13. Theassembly according to claim 2 which includes remote input meansoperatively connected to said drilling fluid circulation system todecrease and then increase the associated pump pressure in a sequence towhich said means to open and close said valve is responsive therebyinitiating the operation of said valve to signal information receivedfrom said transducer within said assembly, to said means to decode anddisplay said detected decreases and increases in said drilling fluidpump pressure..]. .[.14. The assembly according to claim 13 in which theassembly includes a cylindrical casing, a drilling fluid conduitextending through said casing, an annular cavity defined between saidconduit and said casing, said conduit being offset through part of saidcasing, said casing including an electronic holding section within saidcavity, an electro-mechanical holding section within said cavityadjacent said offset, and a power supply holding section within saidcavity, and means to seal off said cavities one from the other, saidcasing being adjacently connected within said drill string..]. .[.15. Aninformation and transmitting assembly for rotary oil well drillingstring comprising in combination a cylindrical casing, a drilling fluidconduit extending through said casing, an annular cavity defined betweensaid conduit and said casing, said conduit being offset through part ofsaid casing, a down-hole assembly installed within said casing, amotorized valve within said casing adjacent said offset, said valvebeing operatively connected between said conduit and the exterior ofsaid casing when said valve is open and shutting off the connectionbetween said conduit and the exterior of said casing, when said valve isclosed, at least one information responsive transducer within saidcasing, electronic means in said casing to translate informationreceived by said transducer into means to open and close said valve in abinary coded decimal system thereby decreasing and increasing thedrilling fluid pressure within said conduit, means remote from saidcasing to detect decreases and increases in drilling fluid pressure andmeans to decode and display said detected decreases and increases indrilling fluid pressures and a source of electrical power within saidcasing..]. .[.16. The assembly according to claim 15 which includesremote input means operatively connected to said drilling fluidcirculation system to decrease and then increase the associated pumppressure in a sequence to which said means to open and close said valveis responsive thereby initiating the operation of said valve to signalinformation received from said transducer within said assembly, to saidmeans to decode and display said detected decreases and increases insaid drilling fluid pump pressure..]. .[.17. The assembly according toclaim 15 which includes a rate of pressure change switch operativelyconnected to said motorized valve whereby said valve only operatesresponsive to a decrease and increase in pressure if the pressure of thedrilling fluid changes a predetermined amount in a fixed time orperiod..]. .[.18. The assembly according to claim 15 in which theassembly includes a cylindrical casing, a drilling fluid conduitextending through said casing, an annular cavity defined between saidconduit and said casing, said conduit being offset through part of saidcasing, said casing including an electronic holding section within saidcavity, an electromechanical holding section within said cavity adjacentsaid offset, and a power supply holding section within said cavity, andmeans to seal off said cavities one from the other, said casing beingadjacently connected within said drill string..]. .[.19. The assemblyaccording to claim 15 in which said electronic means in said assemblytranslates information received by said transducer, into digital signalsfor opening and closing said valve..]. .[.20. The assembly according toclaim 19 which includes remote input means operatively connected to saiddrilling fluid circulation system to decreae and then increase theassociated pump pressure in a sequence to which said means to open andclose said valve is responsive thereby initiating the operation of saidvalve to signal information received from said transducer within saidassembly, to said means to decode and display said detected decreaes andincreases in said drilling fluid pump pressure..]. .[.21. The assemblyaccording to claim 19 which includes said means remote from saidassembly comprising a pressure-to-voltage transducer operativelyconnected to said conduit means between said pump and said hollow drillstring, electronic means to receive and decode signals from saidpressure-to-voltage transducer, operatively connected to said transducerand read-out means operatively connected to said electronic means..]..[.22. The assembly according to claim 21 which includes remote inputmeans operatively connected to said drilling fluid circulation system todecrease and then increase the associated pump pressure in a sequence towhich said means to open and close said valve is responsive therebyinitiating the operation of said valve to signal information receivedfrom said transducer within said assembly, to said means to decode anddisplay said detected decreases and increases in said drilling fluidpump pressure..]. .[.23. The assembly according to claim 15 whichincludes said means remote from said assembly comprising apressure-to-voltage transducer operatively connected to said conduitmeans between said pump and said hollow drill string, electronic meansto receive and decode signals from said pressure-to-voltage transducer,operatively connected to said transducer and read-out means operativelyconnected to said electronic means..]. .[.24. The assembly according toclaim 23 which includes remote input means operatively connected to saiddrilling fluid circulation system to decrease and then increase theassociated pump pressure in a sequence to which said means to open andclose said valve is responsive thereby initiating the operation of saidvalve to signal information received from said transducer within saidassembly, to said means to decode and display said detected decreasesand increases in said drilling fluid pump pressure..]. .Iadd.25. Amethod of telemetering information from a point in a well borehole tothe earth'surface by utilizing a drill string extending into theborehole, and thereby defining a borehole annulus, a drill bit on oneend of the drill string having at least one restrictive nozzle therein,a drilling fluid pump connected to the other end of the drill string, anassembly connected in the drill string and having an unobstructedpassage therethrough, a bypass passageway in the assembly directlycommunicating the unobstructed passage to the borehole annulus and amotorized valve in said bypass passageway, the method comprising thesteps of continuously pumping drilling fluid under pressure through thedrill string, through the unobstructed flow passage and out through thedrill bit nozzle, detecting at a point in the borehole the informationto be telemetered, translating and transmitting said information intodigital signals, using said digital signals in operating said valve toplurally decrease and increase the fluid pressure in the drilling stringby plurally opening and closing the valve in the bypass passageway in acoded decimal format thereby venting a portion of the drilling fluiddirectly into the borehole annulus and bypassing the drill bit nozzlewith said portion of fluid while maintaining continuous unobstructeddrilling fluid flow through the assembly and continuous flow through thedrill bit nozzle, detecting the decreases and increases in the drillingfluid pressure while continuously circulating the drilling fluid anddecoding and displaying at the surface the results of the decreases andincreases in drilling fluid pump pressure. .Iaddend. .Iadd.26. In a welldrilling system which includes a hollow drill string within a boreholethereby defining a borehole annulus, a drill bit on one end of saidhollow drill string, at least one drilling fluid restrictive nozzle insaid bit, a drilling fluid circulation system including a surface pumpand a source of drilling fluid, and conduit means operatively connectingsaid pump to said source of drilling fluid and to the other end of saidhollow drill string; the improvement comprising in combination, adown-hole assembly having means connecting the assembly in the drillstring, a continuous unobstructed passage through said assembly incommunication with said drill string, a bypass passageway in saidassembly directly communicating the unobstructed passage in the assemblyto the borehole annulus and bypassing said drill bit nozzle, a motorizedvalve in the bypass passageway for controlling fluid flow directly tothe associated borehole annulus when the valve is open and to shut offsaid last mentioned flow when said valve is closed, at least oneinformation responsive transducer operatively connected to saidassembly, means in said assembly to translate information received bysaid transducer into means to plurally open and close said valve in acoded decimal sequence thereby plurally decreasing and increasing thedrilling fluid pressure in said sequence, means remote from saidassembly to detect said decreases and increases in drilling fluidpressure, means operatively connected to said detecting means to decodesaid detected decreases and increases in drilling fluid pressure andmeans at the surface to display the decoded information. .Iaddend.